Surface treatment of beverage containers to keep the beverage cool

ABSTRACT

The invention pertains to a method suitable to reduce the heat transfer into a beverage container in order to keep the beverage cool over an extended period of time after taken from the refrigerator. The method is based on a surface treatment of the beverage container which comprises a binder in which phase change material is incorporated. By absorbing latent heat without a temperature increase, the phase change material creates a thermal barrier against heat penetration. The binder with the phase change material contained wherein is applied to the surface of the beverage container, for instance, by spray coating. The coating layer covers most of the container&#39;s surface. A second coating layer which does not contain phase change material is applied on top of the first coating layer in order to provide protection against mechanical stress during high speed filling and packaging.

CROSS-REFERENCES TO RELATED APPLICATIONS

The application claims priority of the U.S. Provisional Patent Application Ser. No. 61/741,826 filed Jul. 27, 2012 entitled “Surface treatment of beverage containers to keep the beverage cool”.

FIELD OF THE INVENTION

The present invention pertains to a method suitable to keep the beverage in the container cool after it is taken from the refrigerator. The method is based on a surface treatment of the beverage container. The surface treatment comprises a binder equipped with phase change material as heat storage mean.

BACKGROUND OF THE INVENTION

Consumer's satisfaction with cold beverages depends often on the initial sensation of coldness and the beverage staying cold while the content is being consumed. However, the beverage in the container warms up quickly after it has been removed from the refrigerator. The heat transfer from the environment into the beverage container occurs many by conduction. The major heat source is the consumer's hand when it holds the container such as a bottle. Another heat source could be the surface of a table where the container is put down between sips. In addition, there could be a convective heat transfer into the container initiated from surrounding air as well as radiant heat transfer when the container is exposed to sunlight.

Insulated holders of the beverage containers used to keep the beverage cool are disclosed, for instance, in U.S. Pat. No. 7,784,759. These holders made, for instance, of neoprene closed cell foam or another insulating material, have not provided the desired solution because they are often perceived as interfering with the experience of holding a cold drink.

Insulative labels attached to beverage containers especially bottles have been disclosed in U.S. Patent Application no. 20080113127 as another solution to keep beverages in containers, such as glass bottles cool. The insulation effect is provided by air gaps between two film layers the labels consist of. However, as disclosed in the said Patent Application, the air layer between the two film layer are only about 2-4 thousands of an inch thick. Therefore, the insulation effect is expected to be only very small.

A new approach to this problem is the surface treatment of the beverage container with phase change material incorporated into a binder.

Phase change material possesses the ability to change its physical state within a certain temperature range. When the melting temperature is obtained in a heating process, the phase change from the solid to the liquid state occurs. During this melting process the phase change material absorbs and stores a large amount of latent heat. In a cooling process of the phase change material, the stored heat is released into the environment in a certain temperature range; and a reverse phase change from the liquid to the solid state takes place.

During the entire melting process, the temperature of the phase change material as well as its surrounding area remains constant. The undesired temperature increase, concomitant during the normal heating process, does not occur. The same is true for the crystallization process. During the entire crystallization process, the temperature of the phase change material also does not change. The high latent heat absorption or latent heat release without any temperature change, is responsible for the phase change materials appeal as a source of heat storage.

In order to contrast the amount of latent heat absorbed by a phase change material during the actual phase change with the amount of sensible heat absorbed in an ordinary heating process, the ice-water phase change process will be used for comparison. When ice melts, it absorbs an amount of latent heat of about 335 J/g. When the water is further heated, it absorbs a sensible heat of only 4 J/g while its temperature rises by one degree C. Therefore, the latent heat absorption during the phase change from ice into water is nearly 100 times higher than the sensible heat absorption during the heating process of water outside the phase change temperature range.

In addition to ice (water), more than 500 natural and synthetic phase change materials are known. These materials differ from one another in their phase change temperature ranges and their latent heat storage capacities.

Applied to a carrier material, the phase change material limits the heat flux through this material as long as the phase change takes place and, therefore, creates a kind of thermal barrier.

The efficiency of this thermal barrier and the duration of the thermal effect depend mainly on the thermal storage capacity of the applied phase change material and its quantity. In addition, the heat transfer characteristics of the carrier material and adjacently arranged materials have an influence on the efficiency of the thermal barrier function.

SUMMARY OF THE INVENTION

The invention pertains to a method to keep a beverage cool over an extended period after the beverage container is taken from the refrigerator. The method is based on a surface treatment of beverage containers such as glass or plastic bottles, and aluminium cans with phase change material. Phase change material is a highly-efficient thermal storage means. It absorbs a large amount of latent heat when its physical state changes from solid to liquid. During the latent heat absorption, the temperature of the phase change material remains constant. By absorbing heat without a temperature increase, the phase change material creates a barrier against heat penetration and, therefore, prevents the transfer of ambient heat into the container. As a result, the temperature of the beverage enclosed in the container does not rise for an extended period of time. Under the scope of the invention, a phase change material mixture has been developed which possesses an appropriate melting point and a high latent heat storage capacity in order to provide a long-lasting thermal effect. The phase change material mixture is incorporated into a binder. The binder with the phase change material is spray-coated or applied otherwise onto the exterior surface of the beverage container, creating a film-like structure. The coating covers most of the container's surface and sticks to it. In a preferred embodiment of the invention, the film-layer containing the phase change material is covered by a protective coating layer in order to withstand mechanical stress during high-speed filling and packaging.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a bottle as one embodiment of a beverage container with the surface treatment containing phase change material applied to its main body.

FIG. 2 is a sectional view of a bottle as one embodiment of a beverage container with the surface treatment containing phase change material applied to its main body and its bottom.

FIG. 3 is a graphical representation of the development of the temperature of the beverage inside containers with and without phase change material surface treatment of the container.

DETAILED DESCRIPTION OF THE INVENTION

In the method of the present invention, a beverage enclosed in a container is kept cool for an extended period of time by the surface treatment of the container with a binder where phase change material is integrated as a thermal storage means.

The binder may comprise, by way of example and not by limitation an acrylic copolymer, an acrylic latex copolymer, a polyurethane copolymer as well as a phenolic resin, a polyester resin, a polyethylene-based resin, a polyvinyl-based resin or an amino-based resin. In the preferred embodiment of the invention a transparent acrylic latex copolymer binder has been used.

Phase change materials comprise, by way of example and not by limitation crystalline alkyl hydrocarbons, salt hydrates, organics such as fatty acids and eutectics. In order to comply with food safety standards, crystalline alkyl hydrocarbons are most suitable for the application in the present invention. Crystalline alkyl hydrocarbons are byproducts of petroleum refining and therefore, relatively inexpensive. They can be mixed to each other in order to realize desired temperature ranges in which the phase change takes place. The thermal behavior of the crystalline alkyl hydrocarbons remains stable also under permanent use.

Based on a variety of preliminary tests, it was figured out that the beverage containers surface must remain at a temperature between 5° C. and 15° C. in order to keep the beverage temperature below a desirable value of 10° C. The beverage temperature has been about 5° C. on average when taken from the refrigerator. Therefore, in the preferred embodiment of the present invention, a mixture of the crystalline alkyl hydrocarbons hexadecane and tetradecane is used. Preferably, the mixture consists of about 10 wt. % to 15 wt. % tetradecane and about 85 wt. % to 90 wt. % hexadecane. By applying this crystalline alkyl hydrocarbon mixture to the binder the latent heat absorption takes place in a temperature range between 5° C. and 15° C. The developed crystalline alkyl hydrocarbon mixture possesses a latent heat storage capacity of about 200 J/g. The selected temperature range as well as the high latent heat storage capacity ensures a sufficient heat absorption effect which limits the heat flux into the beverage container and, therefore, keeps the beverage cool over an extended period of time.

On the other hand, the crystallization of the phase change material mixture takes place in a temperature range between 4° C. and 11° C. This ensures that the phase change material is fully charged under a usual refrigerator temperature between 3° C. and 5° C. within about 30 minutes.

In the preferred embodiment of the present invention, the phase change material mixture has been applied to the selected acrylic latex copolymer binder in a quantity of about 30 wt. % or about 50 vol. %. Incorporated into other binders, the phase change material mixture might be applicable in a quantity of up to 60 wt. %.

After mixing the phase change material mixture which is in a liquid stage at room temperature into the liquid acrylic latex binder, the compound is applied to the exterior surfaces of the various beverage containers, for instance, by spray-coating and sticks to them. In order to accelerate the curing process, the coated containers are placed in a warm environment at a temperature of about 40° C. In this environment, the curing process lasts less than five minutes. The compound could also be applied to the beverage containers by other coating methods, such as dip-coating, belt or roller coating, or screen printing.

The coated layer (2) is preferable applied to the main body, but not the neck of glass bottles or plastic bottles (1) as it is shown in FIG. 1. The content of the bottle neck is usually emptied with the first sip. Therefore, the bottle neck does not need to be cooled. In another embodiment of the invention, shown in FIG. 2, the bottom of bottles is also coated with the binder containing the phase change material, because of a possible contact with a warm table surface. Aluminum cans should be coated on all sides with exception of the lid.

The film-like structure of the coated layer is preferably less than one millimeter thick. The liquid phase change material mixture is cross-linked into the acrylic latex copolymer binder and, therefore, does not leak out while in its liquid stage. In a preferred embodiment of the invention, the film-layer containing the phase change material is covered by a protective layer (3) of a clear coating compound in order to withstand mechanical stress during high-speed filling and packaging. For instance, the same acrylic latex binder without the phase change material could be used for the protective coating. The protective coating layer could also be applied by spray-coating, dip coating, belt or roller coating. Labels as well as external temperature measuring devices can be easily applied to the protective coating layer by a common pressure sensitive adhesive. The protective coating layer is printable. All the materials selected for the surface treatment of the beverage containers are non-toxic and safe in terms of direct food contact.

When placed in the cold environment of a refrigerator, the phase change material included in the coating layer of the beverage container crystallizes. During the crystallization process, the appearance of the phase change material changes from transparent to opaque. Due to the even dispersion of the phase change material throughout the binder, the appearance of the coated film layer changes from transparent to opaque. This, leads to an impression of an icy-touch on the container's surface after the container has been placed in the refrigerator for at least one hour. This feature also serves as an indicator that the beverage has obtained its desired temperature.

On the other hand, when the beverage container is taken from the refrigerator the phase change material absorbs the heat release from the consumer's hand as well as from the environment, the phase change material changes its appearance from opaque to transparent and the icy-touch of the container's surface goes away again.

In order to determine the improvement in cold sensation of the beverage due to the phase change material treatment of the beverage container, a test has been performed. In order to carry out the test, the beverage containers with and without the phase change material treatment were pre-conditioned for 24 hours at 5° C. in a climatic chamber. The prevailing test container were removed from the chamber, were opened and about 40 ml of the beverage was taken out of the test container at the beginning of the test. The temperature of the beverage was measured with a temperature sensor which was dipped into the beverage. The same amount of the beverage was taken from the test container every two minutes and the beverage temperature was then measured. During the test, each test container was held in the hand of the person which conducted the test. The tests were carried out at an ambient temperature of 23° C. and a relative humidity of 50%.

FIG. 3 shows the development of the beverage temperature during the test. The test results shown in FIG. 3 indicate that the beverage inside the beverage container are kept cool over an extended period of time (about twice as long) with the phase change material treatment of the container's exterior surface. 

1. A method to keep a beverage cool over an extended period after the beverage container is taken from the refrigerator realized by a surface treatment of the container comprising: a first layer made of a polymeric compound which contains non-microencapsulated phase change material cross-linked wherein applied to the surface of the container by a coating technique in a first step, and a second layer made of a polymeric compound which does not contain phase change material and which is topically applied to the first layer as a protective coating by a coating technique in a second step, and where the phase change material is used to limit the heat transfer into the beverage container by absorbing latent heat generated from an external heat source such as the consumer's hand and where a visible change in the appearance of the container's surface from icy-white during refrigeration to transparent during room temperature conditions occurs due to the change in the appearance of the phase change material from opaque to transparent during the latent heat absorption.
 2. The method according to claim 1, where the phase change material used to reduce the heat transfer into the beverage container is a mixture of crystalline alkyl hydrocarbons which absorbs latent heat in a temperature range between 5° C. and 15° C.
 3. The method according to claim 1, where the phase change material mixture used to reduce the heat transfer into the beverage container consists of about 10 wt. % to 15 wt. % Tetradecane and 85 wt. % to 90 wt. % Hexadecane.
 4. The method according to claim 1, where the phase change material mixture used to reduces the heat transfer into the beverage container possesses a latent heat storage capacity of about 200 J/g.
 5. The method according to claim 1, where the phase change material mixture used to reduce the heat transfer into the beverage container is integrated in a polymeric compound in a quantity of up to 60 wt. %.
 6. The method according to claim 1, where the phase change material mixture used to reduce the heat transfer into the beverage container is integrated into a polymeric compound which is applied to the surface of the beverage container by spray coating, or dip-coating, or belt or roller coating, or screen printing in a first step.
 7. The method according to claim 1, where a protective layer of a polymeric compound which does not contain phase change material which is applied to the surface of the beverage container on top of the first layer by spray coating, or dip-coating, or belt or roller coating in a second step.
 8. The method according to claim 1, where the surface treatment covers the main body of the beverage container.
 9. The method according to claim 1, where the surface treatment covers the main body and the bottom of the beverage container.
 10. The method according to claim 1, where the beverage containers surface appearance changes from icy-white under low refrigerator temperatures to transparent under room temperature conditions. 